Metallic+Bonds+and+Properties+of+Metals

The bonding in metals is explained by the electron sea model, which proposes that the atoms in a metallic solid contribute their valence electrons to form a "sea" of electrons that surrounds metallic cations. These delocalized electrons are not held by any specific atom and can move easily throughout the solid. A metallic bond is the attraction between these electrons and a metallic cation.

Many of the properties of metals can be explained by means of metallic bonds and delocalized electrons. For example, metals generally have extremely high boiling points because it is difficult to pull metal atoms completely away from the group of cations and attracting electrons. The melting points are considerably lower because of the mobility of the cations and electrons, which can move past each other. Metals are also malleable (able to be hammered into this sheets) and ductile (able to be drawn into wire) because of the mobility of the particles. The delocalized electrons make metals good conductors of electricity. These electrons also interact with light, which is why metals tend to be highly lustrous (luster = metallic shine).

A mixture of elements that has metallic properties is called an alloy. Alloys can be of two basic types. A substitutional alloy is one in which atoms of the original metal are replaced by other atoms of similar size. An interstitial alloy is one in which the small holes in a metallic crystal are filled by other smaller atoms.